Effects of ram velocity on pyramid die extrusion of hollow aluminum profile

During the extrusion process of aluminum alloy, the ram velocity should be well controlled, since it is an important parameter affecting the profile quality and extrusion productivity. The effects of ram velocity on conventional porthole die extrusion have been investigated by some researchers, while its influence on pyramid die extrusion has not been fully clarified. Thus, in this study, the pyramid die extrusion process for producing a hollow rectangular aluminum tube was comprehensively investigated by performing analysis of steady state, transient state, and billet skin tracking. Importantly, the effects of ram velocity on some evaluation parameters of pyramid die extrusion, such as the material flow behavior, extrudate temperature, extrusion force, transverse weld, quality of longitudinal weld, and back end defect, were overall investigated. The results show that the flowing velocity, extrudate temperature, extrusion force, and welding pressure tend to increase as the increase of ram velocity, while the length of transverse weld is reduced at higher ram velocity. However, the effect of ram velocity on the back end defect is quite slight. Moreover, the advantages and shortcomings of pyramid die were also discussed by comparing with the conventional porthole die.